One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,4)(3,7,8,6)(9,10,15,12)(11,17,13,16)(14,20,22,18)(19,23,21,24)(25,26)(27,31)(28,36)(29,34)(30,32)(33,38)(35,40)(37,39)(1,3,5,8)(2,6,4,7)(9,11)(10,16)(12,17)(13,15)(14,19)(18,23)(20,24)(21,22)(25,27,30,29)(26,31,32,34)(28,35,38,37)(33,39,36,40)(10,12)(11,13)(18,20)(19,21)(26,32)(31,34)(33,36)(39,40) involution — undirected(1,4,5,2)(3,7,8,6)(9,12,15,10)(11,17,13,16)(14,20,22,18)(19,24,21,23)(25,26)(27,31)(28,33)(29,34)(30,32)(35,39)(36,38)(37,40)(9,13,15,11)(10,17,12,16)(14,21,22,19)(18,24,20,23)(25,28,30,38)(26,33,32,36)(27,35,29,37)(31,39,34,40)(9,14)(10,18)(11,19)(12,20)(13,21)(15,22)(16,23)(17,24)(25,29,30,27)(26,34,32,31)(28,37,38,35)(33,40,36,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.